Solid compound of rhodium and tellurium and manufacturing process therefor

ABSTRACT

RH2TEO6 CRYSTALLIZED IN THE TETRAGONAL SYSTEM UNDER THE TRIRUTILE FORM, THE PARAMETERS AO AND CO BEING 4.54 AND 9.245 A., RESPECTIVELY, HAVING AN ELECTRICAL CONDUCTIVITY OF 10-4 (OHM.CM)-1 AND AN ENERGY GAP OF 0.04 EV.

United States Patent Int. Cl. H01b 1/08; C01b 19/00; C01g 55/00 US. Cl. 252-518 3 Claims ABSTRACT OF THE DISCLOSURE Rh TeO crystallized in the tetragonal system under the trirutile form, the parameters a and c being 4.54 and 9.245 A., respectively, having an electrical conductivity of 1O (ohm-cm.) and an energy gap of 0.04 ev.

BACKGROUND OF THE INVENTION The present invention relates to a new oxygen-containing compound of rhodium and tellurium, Rh TeO and to a manufacturing process therefor.

SUMMARY OF THE INVENTION The present invention concerns a compound Rh TeO DESCRIPTION OF THE PREFERRED EMBODIMENTS The new compound was prepared from powered Rh O and TeO which were mixed in equimolecular quantities, then comminuted and pelletized.

The starting oxide Rh O was obtained by pyrolysis at 500 C. of pure rhodium nitrate supplied by Fluka, Whereas the TeO was a pure product containing 99% TeO also from Fluka.

In an example, 1.60 g. of pure TeO and 2.54 g. of pure Rh O were mixed together. Then during a period of 1 hour, the mixture was comminuted dry in a steel ball mill lined with tungsten carbide and provided with tungsten carbide balls in order to obtain a well homogenized mixture which was then pelletized in the shape of a disc at room temperature under a pressure of 1000 kg./cm. (6.35 tons per square inch) and heated in air at 750 C. for 24 hours.

The resultant black porous disc of Rh TeO was then comminuted in the aforesaid ball mill until all particles had a particle size of one micron or below.

An X-ray crystallographic analysis carried out on the thus obtained powder showed that the Rh TeO crystallizes in the tetragonal system and belongs to the trirutile type. The unit cell has the following parameters:

a =4.54 A. and c =9.245 A.

The unit cell contains two molecules of Rh TeO The intensities of the lines and the observed interplanar spacings determined in the X-ray crystallographic analysis are given in the following table.

Interplanar Miller indices spacin d Intensity h k l RhzIeO The X-ray crystallographic data show that the thermal treatment of the starting oxides was suficient to obtain a complete loss of identity of the starting oxides with complete conversion to pure Rh TeO in a good crystalline state.

In order to measure the electrical conductivity of the obtained Rh TeO the powder resulting from comminuting the porous disc was again pelletized under the same conditions used for pelletizing the Rh O and TeO mixture. The measured electrical conductivity was in the range of 10* (ohm-cm.) The obtained Rh TeO is thus really a semiconductor and its forbidden gap, or energy gap, amounts to 0.04 ev. The terms forbidden gap and energy gap refer to the distance between the top of the valence band and the bottom of the conduction hand; these terms appear, for instance in Physics and Technology of Semiconductor Devices, by A. S. Grove, pages 91-95 and 1 02.

The manufacturing process for the compound of the present invention is very easy and the operative conditions are easily reproducible.

Used an an anodic operative surface in the electrolysis of sodium chloride, the new compound presents very interesting polarization properties and is very resistant to electrochemical attack under cell conditions.

On account of its properties, the compound Rh TeO of the present invention is very useful for industrial application-s not only as an electrode in various electrochemical processes, but also as an oxidation catalyst in organic chemistry or as a component in composite semiconductive devices.

The starting materials were obtained from Fluka, CH9470 Buchs (Switzerland).

The trademark designation of the rhodium nitrate was Rhodium (III)-nitrat Dihydrat purissimum83 760. The trademark designation of the Te0 was Tellurdioxid purum 99% 86 370. These materials were supplied in a purity grade designated as purissimum which meant for rhodium a chemical analysis in weight-percent as follows:

31.7% Rh and for the TeO a chemical analysis in weight-percent as follows:

99% TeO mF=very strong 90 F=strong m=medium f=weak mt: faint 20 fi=very faint 10 3 Demonstrating the utility of the Rh TeO of the present invention for carrying out the half reaction is the following example. The comminuted product was spread on a titanium plate and subjected to a pressure of 1000 kg./cm. at a temperature of 475 C. for 20 minutes to provide a coating of 5 grams/m. of titanium surface. The coated side of the titanium plate was then subjected, as anode, to two ditferent tests: the first one to measure the overvoltage for the liberation of chlorine under a given anodic current density ka./m. the second one to determine the wear or consumption of noble metal as related to the quantity of evolved chlorine. The term overvoltage is used herein in the same sense as it is used at pages 488-492 of Physical Chemistry by Walter J. Moore, Prentice-Hall Inc., second edition. In the overvoltage test, the coated plate was used as anode for the electrolysis of a brine containing 250 g. NaCl/ kg. of solution, saturated with chlorine at 60 C. and at an approximate pH of 2. Under these conditions, the coated plate of this example showed an overvoltage in the range 400 mv. under an anodic current density of 10 ka./m. In the wear test, the coated plate was used as anode in a cell wih a flowing mercury cathode for the electrolysis of a brine saturated with sodium chloride and chlorine, between 80 and 85 C., under a constant anode-cathode potential diflerence, the test being stopped when the current density was reduced to one half of its initial value (initial value generally was between 30 and 40 ka./m. Under these conditions, the tested plate produced tons of chlorine per square meter of active surface; the rhodium consumption lay below 200 mg. per ton of chlorine produced under an average current density of ka./m.

After the 1.60 g. of Te0 and 2.54 g. of Rh O have been comminuted, the well homogenized mixture has a particle size distribution lower than Lu.

The pelletizing is carried out without any binding additive.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

What is claimed is:

1. Rh TeO crystallized in the tetragonal system under the trirutile form, the parameters a and c being 4.54 and 9.245 A., respectively, having an electrical conductivity of 10" (ohm-cm.)- and an energy gap of 0.04 ev.

2. Rh TeO as claimed in claim 1 and having line intensitim and interplanar spacings as follows:

3. A method for making Rh TeO as claimed in claim 1, comprising the steps of mixing equimolecular quantities of TeO and Rh O comminuting the resulting mixture, pelletizing the result of the step of comminuting, and heating the pellets at 750 C. in an oxidizing atmosphere for a period of time sufiicient to produce Rh TeO' as claimed in claim 1.

References Cited UNITED STATES PATENTS 3,070,421 12/1962 Bayer 23-50 R 3,309,168 3/1967 Bayer 2350 R 3,052,573 9/1962 Dumesnil 2525l8 X 3,324,049 6/1967 Holmes 2525l8 X 3,498,931 3/1970 Rogers et al. 2525l8 3,519,402 7/1970 Hulligen 23315 CHARLES E. VAN HORN, Primary Examiner U.S. Cl. X.R. 423-508, 592 

